The urea derivatives of the formula (II), the triolcarbamate derivatives of formula (III) and the chloroacetanilide derivatives of formula (IV) have long been known as herbicidally active agents and are widely used for plant protection.
It is known however that these active agents, when used in an effective dose for the herbicidal action, also exert a damaging action of varying extent on the cultivated plants.
In the fifties, Hoffmann recognized that some compounds such as 1,8-naphthalic acid and its salts are useful for the decrease in the phytotoxicity of these herbicides [see the U.S. Pat. Nos. 3,131,509 and 3,702,759].
Since that time, the research into antidote compounds has had an intense development.
As a result of the researches carried out in the Stauffer Chemical Company, a novel type of antidotes, i.e. the N,N-disubstituted dichloroacetamides have been recognized [see the German Pat. (DE-PS) Nos. 2,218,097 and 2,350,800]. Since then, several groups of such compounds have been developed which are useful for diminishing the phytotoxicity, although their activity is different.
The antidote effect of a newer type of compounds, i.e. dicarboxylic acid derivatives (esters and amides) is described in the Hungarian Pat. No. 176,669.
Since the mechanism of action of the phytotoxicity of the above-mentioned herbicide agents is various and contraversial and the effect of the antidotes developed up to now is varying, this research is being continued.
In addition to the esters and amines, among the dicarboxylic acid derivatives as antidotes, the dinitrile derivatives [e.g. phthalic acid dinitrile (phthalonitrile) and terephthalic acid dinitrile (terephthalonitrile)] are also mentioned as substances diminishing phytotoxicity (Hungarian Pat. No. 176,669).
Likewise, the antidote effect of dinitrile derivatives is disclosed in the U.S. Pat. No. 4,260,555 and in the Soviet Pat. No. 880,242. The structure of these compounds is rather complicated. Thus, the preparation of them is difficult and expensive.